In the chemical industry, which produces pharmaceuticals and agrochemicals, petrochemicals and polymers, a hydrogenation reaction of a carbon-carbon unsaturated bond or a carbon-nitrogen unsaturated bond comprised in a variety of compounds and converting them to corresponding saturated bond is widely being carried out.
In the field of producing a polymer, for example, a method of selective or partial hydrogenation of a carbon-carbon double bond of a conjugated diene polymer is well known as a useful means of reforming a conjugated diene polymer, and hydrogenated conjugated diene polymers, such as a hydrogenated acrylonitrile butadiene copolymer, are being produced in an industrial volume.
Such a hydrogenated conjugated diene polymer, for instance, is produced according to the following process. That is, an emulsion polymerization of a monomer containing a conjugated diene is performed, the latex obtained by the emulsion polymerization is coagulated and dried, and the base polymer obtained by the coagulation and drying is dissolved in an organic solvent (solvent for hydrogenation reaction), and then a catalyst containing a platinum group metal is added to complete the production process.
As an example of the catalyst containing a platinum group metal used in the above-described process, a platinum group metal and a compound of a platinum group metal may be mentioned. The platinum group metal and the compound of a platinum group metal, for instance, may be used as a supported catalyst by supporting these on carriers. In other case, the compound of a platinum group metal, for instance, the salt of a platinum group metal, may be used as a catalyst for hydrogenation reaction without supporting on carriers.
In the case of using such catalyst containing a platinum group metal, platinum group metal particles of nano-order size exist in a free state (or, a platinum group metal is in an ionized state) in a solution containing a reaction mixture obtained by a hydrogenation reaction, and thus, there was a problem that platinum group metal particles of nano-order size existing in a free state is not able to be recovered. That is, when a supported catalyst is used as a catalyst containing a platinum group metal, by separating the supported catalyst from a solution containing a hydrogenated conjugated diene polymer through filtration or centrifugation, the supported catalyst containing a platinum group metal itself can be recovered. However, platinum group metal particles of nano-order size remain in a free state in the solution containing the hydrogenated conjugated diene polymer, and it is impossible to recover such platinum group metal particles of nano-order size. Meanwhile, in the case of using the salt of a platinum group metal in its original state as a catalyst containing a platinum group metal without supporting on carriers, the platinum group metal particles of nano-order size remain in a free state in the solution containing the hydrogenated conjugated diene polymer, and thus, likewise, the platinum group metal particles of nano-order size is not able to be recovered.
In regards to this, the Patent Document 1 suggests a method of bringing a solution containing a reaction mixture obtained by performing a hydrogenation reaction in the presence of a catalyst containing a platinum group metal into contact with an ion exchange resin having a particular functional group, thereby recovering the catalyst containing a platinum group metal present in the solution. However, in terms of the technology disclosed in the Patent Document 1, there was a problem that in order to recover the catalyst containing a platinum group metal, the solution containing the reaction mixture obtained by a hydrogenation reaction had to be blended with an ion exchange resin and stirred for a long time, and thus, the efficiency was low in recovering the catalyst containing a platinum group metal.